Properties Of Bio-based Composites Research Articles

The Relationship between a Rotational Molding Processing Procedure and the Structure and Properties of Biobased Polyethylene Composites Filled with Expanded Vermiculite

Rotational molding is a technology in which polymeric thin-walled products can be made. The newest descriptions of this technology concern the possibility of obtaining polymer composite materials. There are two main methods of incorporating fillers into a polymer matrix. Dry blending is based on mixing fillers with polymer powders before rotational molding by hand or using automatic mixers. In the melt compounding method, fillers are mixed with the polymer in the preliminary step by melt processing and then grinding or pulverization to obtain polymer powders for rotational molding. This work aimed to investigate the impact of the processing procedure on the structure and properties of biobased composites with expanded vermiculite. Produced rotomolded parts were examined using mechanical tests to assess changes in tensile, flexural, and impact properties. The most significant difference in mechanical properties was noted for samples with 10 wt% expanded vermiculite (EV). The elasticity modulus increases by almost 2 fold when the sample is prepared in a two-step process, the tensile strength is 4-fold higher, the flexural modulus is 3-fold higher, and the flexural strength is 5-fold higher. We also investigated thermomechanical properties in DMA measurement. The void volume content was also measured to control the quality of obtained parts. The porosity of dry blended samples containing more than 2 wt% EV is almost 2-fold higher. Other methods to control quality and structure were optical and scanning electron microscopy used for rotomolded parts and polymer powders. The investigations of rotomolded parts were supplemented with a complete description of used materials, including the particle size distributions of polymer powders and filler. Analysis of the thermal properties and chemical structure was also performed despite all the mechanical tests. The emerging conclusions from the research clearly show that the two-step process allows for achieving a more beneficial mechanical performance of the composites made of the biobased polymer in rotational molding technology.

Synthesis and Properties of Bio-Based Composites from Vegetable Oils and Starch

Natural polymers, such as starch, and polymers derived from renewable resources, such as vegetable oils, have been considered as alternatives to petroleum-based plastics during recent decades, due to environmental concerns. Indeed, these materials can offer a variety of advantages, such as low cost, wide availability, carbon neutrality, elevated thermal stability, and easily tunable mechanical properties. However, some of these polymers alone exhibit poor mechanical properties, making them not suitable for some applications. Hence, the reinforcement of these bio-based polymers with other materials is often considered to overcome this challenge. In this work, thermosetting composites based on tung and linseed oil resins were prepared using starch as reinforcement. Analyses from Soxhlet extractions showed that the higher the concentration of tung oil in comparison to linseed oil in the resins, the lower the mass of unreacted material, leading to an optimum resin entirely based on tung oil. Dielectric analysis (DEA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) indicated that the polymerization was completed in 3 h 20 min, at 140 °C, and that the composites were thermally stable until 270 °C. Finally, dynamic mechanical analysis (DMA) confirmed that the addition of starch to the resins increased the room temperature storage modulus (E′25) from 94 MPa to 893 MPa. Composites prepared with a resin formulation that did not contain a compatibilizer exhibited E′25 of 441 MPa. The composites investigated in this work are promising candidates for applications that require improved mechanical properties.

Mechanical characterization and modeling of poly (β-hydroxybutyrate)-co-poly(β-hydroxyvalerate)-Alfa fiber-reinforced composites

The mechanical properties of biobased composites of poly(β-hydroxybutyrate)-co-poly(β-hydroxyvalerate) biopolymer continuously reinforced with unidirectional Alfa fibers are investigated via tensile testing of oriented composite laminates. Simple mechanical models for the elastic stiffness, strength, and nonlinear hardening of the biobased composites are proposed with an emphasis on techniques that only require the independent properties of the fiber and matrix to facilitate composite design. Rule of mixtures (ROM) approaches are found to effectively predict the elastic properties of the composites but generally overestimate strength. Modified ROM approaches that discount the contribution of the matrix in the fiber loading direction and the contribution of the fiber in the transverse loading direction provide the most accurate strength predictions. Apparent elastic properties for composites with varying fiber orientations are predicted using a modified orthotropic laminate plate method which was found to overestimate composite stiffness in off-axis loading directions. Postyield nonlinear hardening is modeled using a calibrated continuum yield and plasticity model and demonstrated to provide a close match of the experimental results. POLYM. COMPOS., 35:1758–1766, 2014. © 2014 Society of Plastics Engineers

Effect of Alkali Treatment on Physical Properties of Bio-Based Composites

In the present study, bast kenaf natural fibres were alkali-treated to determine the effect of treatment on the physical properties of natural fibre-reinforced biocomposites. Both unsaturated polyesters and bio-polyester resins were used as matrices. Other resin systems were studied as well, including a resin made with low VOC, fatty acid-derived reactive diluents. After all the biocomposites had been fabricated via compression moulding, it was observed that the incorporation of alkali-treated fibres in the biocomposites decreased the flexural and thermo-mechanical properties of the biocomposites. It was also observed that mercerizing the kenaf aided in reducing the moisture absorption by 30% and increasing the compressive strength by ∼30% compared to that of the untreated biocomposites. The property changes were believed to be the result of crystallinity changes in the kenaf as a result of the treatment.